these are two circuit one with NPN transistor and other without transistor you can use any small gain transistors like 2n39042n2222bc547 these are very common

hi miraheng you can use a piezo it will work the same for lighting a bulb at the output you need to connect a bulb 6v relay at output but this is good for lower frequency switching but for faster switching at output we need to do something else ...like using power transistors etc

Thanks for letting me know PNP transistor is optional here if we need to derived a big load rather than LED .like motors OR many LEDs .But for a single led it's optional here .I forget to mention in my post but don't worry it will be updated soon.

Hi tater zoid I want to know thatIs it safer to post my images on my instructable which I already used in making YouTube video ????coz I THINK YouTube video checking software will find my images on instructable will banned my AdSenseplz tell me about that ....Thanks...